Abstract: A method and device for determining the temperature of a sample, wherein a probing light beam is directed onto the sample whereby at least two partial beams of the probing light pass through paths of different lengths inside the sample by backscattering or reflecting the beams from at least two different depths in the sample, returning the partial beams to an analysis unit, and producing an interference pattern in the analysis unit by means of an interferometric device which uses one light beam as a reference for evaluating the interference pattern in an evaluating unit, wherein the signal intensity of the partial beam is determined counter to the optical path and the temperature displacement and temperature of the sample are determined by the temperature adjustment of the signal intensity.

Abstract: An optical method, and an optical device based on a laser source for implementing an optical method, for nonintrusively measuring the temperature of a flowing liquid by using the fluorescence induced by a laser beam in a measurement volume of the liquid, uses a single temperature-sensitive fluorescent tracer and at least two separate spectral detection windows on the tracer, after molecular dilution of the tracer in the liquid medium.